Heat transfer system, fluid, and method

ABSTRACT

Disclosed herein is a heat transfer system comprising a circulation loop defining a flow path for a heat transfer fluid, and a heat transfer fluid comprising a liquid coolant, a siloxane corrosion inhibitor of formula R3-Si—[O—Si(R)2]x-OSiR3, wherein R is independently an alkyl group or a polyalkylene oxide copolymer of 1 to 200 carbons, x is from 0 to 100, and further wherein at least one alkyl group and at least one polyalkylene oxide copolymer are present, and a non-conductive polydiorganosiloxane antifoam agent, wherein the conductivity of the heat transfer fluid is less than about 100 μS/cm, and wherein the heat transfer system comprises aluminum, magnesium, or a combination thereof, in intimate contact with the heat transfer fluid.

This application is a continuation-in-part of application Ser. No.11/222,024, filed Sep. 8, 2005, which claims the benefit of U.S.provisional application No. 60/607,898, filed Sep. 8, 2004, both ofwhich are incorporated by reference herein in their entirety. Thisapplication also claims the benefit of U.S. provisional application No.61/080,033 filed on Jul. 11, 2008, which is incorporated by referenceherein in its entirety.

BACKGROUND

This disclosure generally relates to a heat transfer system, heattransfer fluid, and heat transfer method.

The operation of a power source generates heat. A heat transfer system,in communication with the power source, regulates the generated heat,and ensure that the power source operates at an optimum temperature. Theheat transfer system generally comprises a heat transfer fluid thatfacilitates absorbing and dissipating the heat from the power source.Heat transfer fluids, which generally comprise water and a glycol, arein intimate contact with one or several metallic parts that are prone tocorrosion. Thus, several corrosion inhibitors are added to the heattransfer fluid in order to protect the metallic parts from corrosion.Traditional heat transfer fluids can exhibit extremely highconductivities, often in the range of 3000 microsiemens per centimeter(PS/cm) or more. This high conductivity produces adverse effects on theheat transfer system by promoting corrosion of metal parts, and also inthe case of power sources where the heat transfer system is exposed toan electrical current, such as in fuels cells or the like, the highconductivity can lead to short circuiting of the electrical current andto electrical shock.

Aluminum, magnesium, and their alloys, are increasingly used in themanufacture of several components of a heat transfer system. They areadvantageous due to their light weight, high strength, and relative easeof manufacture, among others. Aluminum, magnesium, and their alloys canbe used in heat transfer systems of internal combustion engines andalternative power sources. However, magnesium, aluminum, and theiralloys are highly susceptible to corrosion when in contact withtraditional heat transfer fluids with high conductivity. In addition,the foaming of traditional heat transfer fluids further contributes tothe corrosion of aluminum, magnesium, and their alloys.

Therefore, a need exists for heat transfer systems and fluids intendedfor use therein, wherein the heat transfer systems comprise aluminum,magnesium, or their alloys, in intimate contact with the heat transferfluid. The heat transfer fluids advantageously have low conductivity andgood foaming properties.

SUMMARY

The above-described and other drawbacks are alleviated by a heattransfer system, comprising a circulation loop defining a flow path fora heat transfer fluid, and a heat transfer fluid comprising a liquidcoolant, a siloxane corrosion inhibitor of formulaR3-Si—[O—Si(R)2]x-OSiR3, wherein R is independently an alkyl group or apolyalkylene oxide copolymer of 1 to 200 carbons, x is from 0 to 100,and further wherein at least one alkyl group and at least onepolyalkylene oxide copolymer are present, and a non-conductivepolydiorganosiloxane antifoam agent, wherein the conductivity of theheat transfer fluid is less than about 100 μS/cm, and wherein the heattransfer system comprises aluminum, magnesium, or a combination thereof,in intimate contact with the heat transfer fluid.

In one embodiment, a heat transfer fluid comprises a liquid coolant, asiloxane corrosion inhibitor of formula R3-Si—[O—Si(R)2]x-OSiR3, whereinR is independently an alkyl group or a polyalkylene oxide copolymer of 1to 200 carbons, x is from 0 to 100, and further wherein at least onealkyl group and at least one polyalkylene oxide copolymer are present,and a non-conductive polydiorganosiloxane antifoam agent, wherein theconductivity of the heat transfer fluid is less than about 100 μS/cm.

In another embodiment, a heat transfer method comprises contacting aheat transfer system with a heat transfer fluid, wherein the heattransfer system comprises a circulation loop defining a flow path forthe heat transfer fluid, and aluminum, magnesium, or a combinationthereof, wherein the heat transfer fluid comprises a liquid coolant, asiloxane corrosion inhibitor of formula R3-Si—[O—Si(R)2]x-OSiR3, whereinR is independently an alkyl group or a polyalkylene oxide copolymer of 1to 200 carbons, x is from 0 to 100, and further wherein at least onealkyl group and at least one polyalkylene oxide copolymer are present,and a non-conductive polydiorganosiloxane antifoam agent, wherein theconductivity of the heat transfer fluid is less than about 100 μS/cm,and wherein the aluminum, magnesium, or combination thereof is inintimate contact with the heat transfer fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alikein several FIGURES:

FIG. 1 is a schematic diagram of one embodiment of the heat transfersystem; and

FIG. 2 is a schematic diagram of another embodiment of the heat transfersystem.

DETAILED DESCRIPTION

Surprisingly, the present inventors have discovered that a heat transferfluid comprising a liquid coolant, a siloxane corrosion inhibitor, and anon-conductive polydiorganosiloxane antifoam agent, is an effective lowconductivity heat transfer fluid that is advantageous for use in heattransfer systems where the heat transfer fluid is in intimate contactwith aluminum, magnesium, or their alloys, and/or with power sourceswhere the heat transfer fluid is exposed to an electrical current. Theconductivity of the heat transfer fluid is advantageously less thanabout 100 μS/cm. In one advantageous embodiment, the heat transfer fluidfurther comprises an azole.

As used herein, “aluminum” refers to aluminum metal, alloys thereof, ora combination thereof, and “magnesium” refers to magnesium metal, alloysthereof, or a combination thereof.

The liquid coolant comprises an alcohol, water, or a combination of analcohol and water. It is advantageous to use deionized water,demineralized water, or a combination thereof, which generally exhibit aconductivity lower than that of water which has not been deionized ordemineralized. The heat transfer fluid can be a concentrated heattransfer fluid, that is, a heat transfer fluid comprising a liquidcoolant consisting essentially of alcohols. Concentrated heat transferfluids are advantageous for storage and shipping. Concentrated heattransfer fluids can, if desired, be combined with water prior to orafter use in the heat transfer system. The heat transfer fluid can, onthe other hand, be a diluted heat transfer fluid, that is, a heattransfer fluid comprising alcohols and water. Both concentrated anddiluted heat transfer fluids are suitable for use in the heat transfersystem. In one embodiment, the heat transfer fluid comprises aconcentrated heat transfer fluid. In another embodiment, the heattransfer fluid comprises a diluted heat transfer fluid.

Water can be present in the heat transfer fluid in an amount of about0.01 to about 90 weight percent (wt %), based on the total weight of theheat transfer fluid. Specifically, water can be present in the heattransfer fluid in an amount of about 0.5 to about 70 wt %, and morespecifically about 1 to about 60 wt %, based on the total weight of theheat transfer fluid. The heat transfer fluid can be free of water.

The alcohol comprises monohydric alcohols, polyhydric alcohols, ormixtures of monohydric and polyhydric alcohols. Non-limiting examples ofmonohydric alcohols include methanol, ethanol, propanol, butanol,furfurol, tetrahydrofurfurol, ethoxylated furfurol, alkoxy alkanols suchas methoxyethanol, and the like, and combinations comprising at leastone of the foregoing monohydric alcohols. Non-limiting examples ofpolyhydric alcohols include, ethylene glycol, diethylene glycol,triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol (or1,3-propanediol), dipropylene glycol, butylene glycol, glycerol,glycerol-1,2-dimethyl ether, glycerol-1,3-dimethyl ether, monoethyletherof glycerol, sorbitol, 1,2,6-hexanetriol, trimethylol propane, and thelike, and combinations comprising at least one of the foregoingpolyhydric alcohols.

The alcohol can be present in the heat transfer fluid in an amount ofabout 10 to about 99.9 wt %, based on the total weight of the heattransfer fluid. Specifically, the alcohol can be present in the heattransfer fluid in an amount of about 30 to about 99.5 wt %, and morespecifically about 40 to about 99 wt %, based on the total weight of theheat transfer fluid.

Siloxane corrosion inhibitors comprise polysiloxanes or organosilanecompounds comprising a silicon-carbon bond, or combinations thereof.Suitable polysiloxanes are those of the formula R3-Si—[O—Si(R)2]x-OSiR3wherein R is independently an alkyl group or a polyalkylene oxidecopolymer of 1 to 200 carbons and x is from 0 to 100, more specifically2 to 90, more specifically 3 to 80, more specifically 4 to 70, and evenmore specifically 5 to 60.

In one exemplary embodiment, the siloxane corrosion inhibitors comprisepolysiloxanes or organosilane compounds comprising a silicon-carbonbond, or a combination thereof, and further comprising at least onegroup that is a polyalkylene oxide copolymer of one or more alkyleneoxides having from 2 to 6 carbons, specifically from 2 to 4 carbons. Inanother exemplary embodiment, the siloxane corrosion inhibitor is of theformula R3-Si—[O—Si(R)2]x-OSiR3 wherein R is independently an alkylgroup or a polyalkylene oxide copolymer of 1 to 200 carbons and x is asdiscussed above, and further wherein at least one alkyl group and atleast one polyalkylene oxide copolymer.

Non-limiting examples of commercially available polysiloxanes for useherein include the SILWET siloxanes from GE Silicones/OSi Specialties,and other similar siloxane-polyether copolymers available from DowCorning or other suppliers. In one exemplary embodiment, siloxanecorrosion inhibitors comprise SILWET L-77, SILWET L-7657, SILWET L-7650,SILWET L-7600, SILWET L-7200, SILWET L-7210 or the like.

Organosilane compounds comprise a silicon-carbon bond capable ofhydrolyzing in the presence of water to form a silanol, that is, acompound comprising silicon hydroxide. Organosilane compounds can be ofthe formula R′Si(OZ)3 wherein R′ and Z are independently an aromaticgroup, an alkyl group, a cycloalkyl group, an alkoxy group, or analkenyl group, and can comprise a heteroatom such as N, O, or the like,in the form of functional groups such as amino groups, epoxy groups, orthe like. In one embodiment, R′ is an aromatic group, an alkyl group, acycloalkyl group, an alkoxy group, or an alkenyl group, and can comprisea heteroatom such as N, O, or the like, in the form of functional groupssuch as amino groups, epoxy groups, or the like, and Z is a C1-C5 alkylgroup.

Non-limiting examples of commercially available organosilane compoundsfor use herein include the SILQUEST and FORMASIL surfactants from GESilicones/OSi Specialties, and other suppliers. In an exemplaryembodiment, siloxane corrosion inhibitors comprise FORMASIL 891,FORMASIL 593, FORMASIL 433, SILQUEST Y-5560(polyalkyleneoxidealkoxysilane), SILQUEST A-186(2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane), SILQUEST A-187(3-glycidoxypropyltrimethoxysilane), or other SILQUEST organosilanecompounds available from GE Silicones, Osi Specialties or othersuppliers and the like.

Non-limiting examples of other organosilane compounds for use hereininclude 3-aminopropyltriethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, octyltriethoxysilane,vinyltriethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane,3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane,isobutyltrimethoxysilane, phenyltrimethoxysilane,methyltrimethoxysilane, and those organosilane compounds having astructure similar to the foregoing, but varying numbers of carbon atoms.

The siloxane corrosion inhibitor can be present in the heat transferfluid in an amount of about 0.01 to about 10 wt %, more specificallyabout 0.02 to about 2 wt %, based on the total weight of the heattransfer fluid.

The non-conductive polydiorganosiloxane antifoam agents comprise anypolydiorganosiloxane antifoam agents. Specifically, the non-conductivepolydiorganosiloxane antifoam agents are those where the terminal groupsat the molecular chain are selected from a trimethylsilyl group, adimethylhydroxysilyl group, and a combination thereof. In one exemplaryembodiment, the polydiorganosiloxane is polydimethylsiloxane. Theseantifoam agents are effective at preventing the formation of foam in theheat transfer fluid and/or eliminating foam that formed in the heattransfer fluid. The polydiorganosiloxane antifoam agents areadvantageously emulsion based antifoam agents

In one exemplary embodiment, the polydimethylsiloxanes for use hereinhas the formula (CH3)3SiO—(SiCH3)2O)m-Si(CH3)3, where m is from 1 to30,000.

Specifically, the polydiorganosiloxanes have a kinematic viscosity ofabout 5 to about 100 million mm2/sec at 25° C. More specifically, thekinematic viscosity of the polydimethylsiloxanes is about 10 to about1,000,000 mm2/sec at 25° C. and the average molecular weight is about1000 to about 200,000 Daltons.

Polydiorganosiloxanes for use herein also include polydiethylsiloxanes,polydimethyl polydiphenyl siloxane copolymers,polydimethyl-poly(chloropropyl methyl)siloxanes, and a combinationthereof.

Other polydiorganosiloxanes for use herein have the formula(CH3)3SiO—(SiCH3)2O)x-(CH3GSiO)y-Si(CH3)3, wherein G comprises analkyleneoxide or a polyoxyalkylene group. Non-limiting examples of Ginclude oxyalkylene groups having the formula —(CH2)z(OCH2CH2)mOH,—(CH2)z(OCH2CH2CH2)mOH, —(CH2)zO(OCH2CH2)mH, —(CH2)zO(OCH2CH2CH2)mH,—(CH2)z(OCH2CH2CH2)k(OCH2CH2)lOH, —(CH2)zO(OCH2CH2CH2)k(OCH2CH2)lH,—(CH2)z(OCH2CH2)k[OCH2C(CH3)H]lOH, —(CH2)z(OCH2CH2)mOCH3,—(CH2)z(OCH2CH2)k[OCH2C(CH3)H]lOCH3, —(CH2)z(OCH2CH2)mOC(O)CH3,—(CH2)z(OCH2CH2CH2)mOCH3, and —(CH2)z(OCH2CH2)k[OCH2C(CH3)H]lOC(O)CH3,wherein x is an integer of 1 to 700, y is an integer of 1 to 60, z is aninteger of 2 to 15, and m, k and l are integers of 1 to 40. Mixture ofthe above-described polydiorganosiloxanes can also be used.

The polydiorganosiloxane antifoam agent can further comprise up to about20 wt % of a finely divided filler. Non-limiting examples of the finelydivided filler include fumed, precipated, and plasmatic TiO2, Al2O3,Al2O3/SiO2, ZrO2/SiO2, and SiO2. Hydrocarbon waxes, triglycerides, longchain fatty alcohols, fatty acid esters and finely divided polyolefinpolymers, such as polypropylene, polyisobutylene, are additionalexamples of fillers for use herein. The finely divided filler can behydrophilic or hydrophobic. The filler can be hydrophobed duringmanufacturing of the antifoam or independently. Various grades of silicahaving a particle size of several nanometers to several microns and aspecific surface area of about 40 to about 1000 m2/g, more specificallya specific surface area of about 50 to about 400 m2/g, are commerciallyavailable and suitable for use as the filler in the polydiorganosiloxanebased antifoams.

In one exemplary embodiment, hydrophobized silica having a specificsurface area of about 50 to about 350 m2/g is used as the filler.Non-limiting examples of silica fillers for use herein include AEROSIL R812, and R 812S from Evonik Degussa (Essen, Germany), TULLANOX 503 and1080 from Tulco (MA, U.S.A.), and similar products from other suppliers.

The polydiorganosiloxane antifoam agent can further comprise up to 20 wt% of a hydrophobic oil. Non-limiting examples of the hydrophobic oilinclude mineral oil, hydrocarbon oils derived from carbonaceous sources,such as petroleum, shale, and coal, and equivalents thereof. Mineraloils include heavy white mineral oil which is high in paraffin content,light white mineral oil, petroleum oils such as aliphatic or wax-baseoils, aromatic and asphalt-base oils, mixed-base oils, petroleum derivedoils such as lubricants, engine oils, machine oils, and cutting oils,and medicinal oils such as refined paraffin oil. The mineral oils areavailable commercially from several suppliers, including, but notlimited to, Exxon Company (Houston, Tex.), and Shell Chemical Company(Houston, Tex.). In one exemplary embodiment, the mineral oil has adynamic viscosity of about 1 to about 20 centipoise (“cP”, 1 cP=1 mPa·s)at 25° C.

The polydiorganosiloxane antifoam agent can further comprise othercomponents, such as polyalkylenoxide, water, alkylene glycol,surfactants, antiseptic agents, and biocides, up to about 95 wt %.

Non-limiting examples of commercially available non-conductivepolydimethylsiloxane based antifoam agents and emulsions thereof includePC-5450NF from Performance Chemicals LLC, XD-55 and XD-56 from CNCInternational, and Y-14865 from Momentive Performance Materials.

The non-conductive polydiorganosiloxane antifoam agent can be present inthe heat transfer fluid in an amount of about 1 to about 3000 parts permillion (ppm), specifically about 100 to about 2000 ppm, morespecifically about 200 to about 1000 ppm, based on the total weight ofthe heat transfer fluid.

In one advantageous embodiment, the heat transfer fluid furthercomprises an azole. Azoles for use herein include five-memberedheterocyclic compounds having 1 to 4 nitrogen atoms as part of theheterocycle. Non-limiting examples of azoles include pyrroles,pyrazoles, imidazoles, triazoles, thiazoles and tetrazoles according toformulas (I)-(IV):

wherein R¹ and R² are independently a hydrogen atom, a halogen atomsuch, a C₁₋₂₀ alkyl or cycloalkyl group, SR³, OR³, or NR³ ₂, wherein R³is independently a hydrogen atom, a halogen atom, or a C₁₋₂₀ alkyl orcycloalkyl group, X is independently N or CR², and Y is independently Nor CR¹.

Non-limiting examples of azoles include pyrrole, methylpyrrole,pyrazole, dimethylpyrazole, benzotriazole, tolyltriazole, methylbenzotriazole such as 4-methyl benzotriazole and 5-methyl benzotriazole,butyl benzotriazole, mercaptobenzothiazole, benzimidazole,halo-benzotriazole such as chloro-methylbenzotriazole, tetrazole, methyltetrazole, mercapto tetrazole, thiazole, 2-mercaptobenzothiazole and thelike. In one embodiment, the azole comprises benzotriazole,tolyltriazole, mercaptobenzothiazole, or a combination thereof. In oneexemplary embodiment, the azole comprises benzotriazole. In anotherexemplary embodiment, the azole comprises tolyltriazole.

The azole can be present in the heat transfer fluid in an amount of0.0001 to about 10 wt %, specifically about 0.01 to about 8 wt %, morespecifically about 0.5 to about 4 wt %, based on the total weight of theheat transfer fluid.

The heat transfer fluid can further comprise additional corrosioninhibitors that are non-ionic. Non-limiting examples of these additionalcorrosion inhibitors include fatty acid esters, such as sorbitan fattyacid esters, polyalkylene glycols, polyalkylene glycol esters,copolymers of ethylene oxide and propylene oxide, polyoxyalkylenederivatives of sorbitan fatty acid esters, or the like, or combinationsthereof. The average molecular weight of additional corrosion inhibitorsis from about 55 to about 300,000 daltons, and more specifically fromabout 110 to about 10,000 daltons. Non-limiting examples of sorbitanfatty acid esters include sorbitan monolaureates such as SPAN 20,ARLACEL 20, or S-MAZ 20M1, sorbitan monopalmitates such as SPAN 40 orARLACEL 40, sorbitan monostearates such as SPAN 60, ARLACEL 60, or S-MAZ60K, sorbitan mono-oleate such as SPAN 80 or ARLACEL 80, sorbitanmonosesquioleate such as SPAN 83 or ARLACEL 83, sorbitan trioleate suchas SPAN 85 or ARLACEL 85, sorbitan tristearate such as S-MAZ 65K,sorbitan monotallate such as S-MAZ 90, or the like, or combinationsthereof. Non-limiting examples of polyalkylene glycols includepolyethylene gycols, polypropylene glycols, and combinations thereof.Non-limiting examples of polyethylene glycols for use herein includethose available commercially under the tradename CARBOWAX polyethylenegycols and methoxypolyethylene glycols from Dow Chemical Company, suchas CARBOWAX PEG 200, 300, 400, 600, 900, 100, 1450, 3350, 4000, or 8000,under the trademark PURACOL polyethylene glycols from BASF Corporation,such as PURACOL E 200, 300, 400, 600, 900, 1000, 1450, 3350, 4000, 6000,or 8000. Non-limiting examples of polyalkylene glycol esters includemono- or di-esters of various fatty acids, such as those available underthe tradename MAPEG polyethylene glycol esters from BASF Corporation,such as MAPEG 200 mL or PEG 200 Monolaureate, MAPEG 400 DO or PEG 400Dioleate, MAPEG 400 MO or PEG 400 Mono-oleate, and MAPEG 500 DO or PEG600 Dioleate. Non-limiting examples of copolymers of ethylene oxide andpropylene oxide include various PLURONIC and PLURONIC R block copolymersurfactants such as those available under the trademark DOWFAX non-ionicsurfactants, UNCON(RO) fluids and SYNALOX lubricants from DOW Chemical.Non-limiting examples of polyoxyalkylene derivatives of a sorbitan fattyacid ester include polyoxyethylene 20 sorbitan monolaurate availableunder the tradename TWEEN 20 or T-MAZ 20, polyoxyethylene 4 sorbitanmonolaurate available under the tradename TWEEN 21, polyoxyethylene 20sorbitan monopalmitate available under the tradename TWEEN 40,polyoxyethylene 20 sorbitan monostearate available under the tradenamesTWEEN 60 and T-MAZ 60K, polyoxyethylene 20 sorbitan mono-oleateavailable under the tradename TWEEN 80 or T-MAZ 80, polyoxyethylene 20tristearate available under the tradename TWEEN 65 or T-MAZ 65K,polyoxyethylene 5 sorbitan mono-oleate available under the tradenameTWEEN 81 or T-MAZ 81, polyoxyethylene 20 sorbitan trioleate availableunder the tradename TWEEN 85 or T-MAZ 85K, and the like.

The heat transfer fluid can further comprise colloidal silica. Colloidalsilica for use herein is of an average particle size of about 1nanometer (nm) to about 200 nm, more specifically from about 1 nm toabout 100 nm, and even more specifically from about 1 nm to about 40 nm.The colloidal silica is advantageous as a secondary corrosion inhibitor,and can sometimes improve the heat transfer properties of the heattransfer fluid. While not wishing to be bound by theory, it is believedthat the use of silica of a particular average particle size providesimprovements in heat transfer efficiency and/or heat capacity byproviding a large surface area for contact with the liquid coolant.

Non-limiting examples of colloidal silica include LUDOX from DuPont orGrace Davidson, NYACOL or BINDZIL from Akzo Nobel or Eka Chemicals,SNOWTEX from Nissan Chemical. Other suppliers of suitable colloidalsilica include Nalco and the like.

The colloidal silica can be present in the heat transfer fluid in anamount of 0.01 to about 10,000 ppm, more specifically of about 0.02 toabout 2000 ppm, and even more specifically about 0.1 to about 1000 ppm,based on the total weight of the heat transfer fluid.

Other additional corrosion inhibitors include cyclohexanoic carboxylatesderived from long chain fatty acids, as well as salts and estersthereof, and amine compounds, such as mono-, di-, and triethanolamine,morpholine, benzylamine, cyclohexylamine, dicyclohexylamine, hexylamine,2-amino-2-methyl-1-propanol, diethylethanolamine, diethylhydroxylamine,2-dimethylaminoethanol, dimethylamino-2-propanol, and3-methoxypropylamine. These additional corrosion inhibitors can be addedto the heat transfer fluid, with the proviso that they do not produceadverse effects. The other additional corrosion inhibitors can bepresent in the heat transfer fluid in an amount of 0.01 wt % to about 5wt %, based on the total weight of the heat transfer fluid.

In certain embodiments, it can be advantageous if the heat transferfluid comprises a tetraalkylorthosilicate ester. Thetetraalkylorthosilicate ester comprises a C1-C20 alkyl group,non-limiting examples of which include tetramethylorthosilicate,tetraethylorthosilicate, and the like. The tetraalkylorthosilicate estercan be present in the heat transfer fluid in an amount of 0.01 wt % toabout 5 wt %, based on the total weight of the heat transfer fluid.

The corrosion inhibiting heat transfer fluid can further comprise anon-conductive colorant that is a non-ionic or a weakly ionic speciessoluble or dispersible in the liquid coolant at the concentration of thecolorant required to provide coloring of the heat transfer fluid.

In one embodiment, the non-conductive colorant is substantially free offunctional groups that will form an ionic species due to hydrolysis inan aqueous alcohol or alkylene glycol solution. In another embodiment,the non-conductive colorant is substantially free of functional groupsselected from the group consisting of carboxylate groups, sulfonategroups, phosphonate groups, quaternary amines, groups that carry apositive charge, and groups that carry a negative charge. Non-limitingexamples of groups that carry a positive charge include Na+, Cu2+,—NR33+ where R3 is H, C1-C20 alkyl groups or aromatic ring containinggroups, Fe3+, the like, and combinations thereof. Non-limiting examplesof groups that carry a negative charge include Cl−, Br−, I−, and thelike, and combinations thereof.

Non-limiting examples of non-conductive colorants include a chromophoresuch as anthraquinone, triphenylmethane, diphenylmethane, azo containingcompounds, diazo containing compounds, triazo containing compounds,xanthene, acridine, indene, phthalocyanine, azaannulene, nitroso, nitro,diarylmethane, triarylmethane, methine, indamine, azine, oxazine,thiazine, quinoline, indigoid, indophenol, lactone, aminoketone,hydroxyketone, stilbene, thiazole, a conjugated aromatic groups, aconjugated heterocyclic group (e.g., stilbene,bis-triazenylaminostilbene, pyrazoline, and/or coumarin type molecule ora combination thereof), a conjugated carbon-carbon double bond (e.g.,carotene), and a combination thereof. In one exemplary embodiment, thenon-conductive colorants will comprise a diarylmethane, triarylmethane,triphenylmethane, diphenylmethane, a conjugated aromatic group, an azogroup, or a combination thereof. In an advantageous embodiment, thenon-conductive colorant comprises a chromophore comprising a conjugatedaromatic group.

The non-conductive colorant can comprise alkyleneoxy or alkoxy groupsand a chromophore such as described above. In one embodiment, thechromophore is selected from the group consisting of anthraquinone,triphenylmethane, diphenylmethane, azo containing compounds, diazocontaining compounds, triazo containing compounds, compounds comprisingone or more conjugated aromatic groups, one or more conjugatedheterocyclic groups, and combinations thereof.

In one embodiment, non-conductive colorants can be of the formulaR4{Ak[(E)nR5]m}y wherein R4 is an organic chromophore selected from thegroup consisting of anthraquinone, triphenylmethane, diphenylmethane,azo containing compounds, diazo containing compounds, triazo containingcompounds, xanthene, acridine, indene, thiazole, compounds comprisingone or more conjugated aromatic groups, one or more conjugatedheterocyclic groups, or combinations thereof, A is a linking moiety andis selected from the group consisting of O, N or S, k is 0 or 1, E isselected from the group consisting of one or more C1-C8 alkyleneoxy oralkoxy groups, n is 1 to 100, m is 1 or 2, y is 1 to 5, and R5 isselected from the group consisting of H, C1-C6 alkyl or C1-C8 alkoxygroups, or combinations thereof.

In one exemplary embodiment, the non-conductive colorants are of theformula R4{Ak[(E)nR5]m}y wherein R4 is as described above, A is N or O,k is 0 or 1, E is a C2-C4 alkyleneoxy group, n is from 1 to 30, m is 1or 2, y is 1 or 2, and R5 is H, a C1-C4 alkyl group, or a C1-C6 alkoxygroup.

The non-conductive colorants can be prepared by various known methodssuch as those described in U.S. Pat. No. 4,284,729, U.S. Pat. No.6,528,564 or other patents issued to Milliken & Company, Spartanburg,S.C., USA.

For example, suitable colorants can be prepared by converting a dyestuffintermediate containing a primary amino group into the correspondingpolymeric compound and employing the resulting compound to produce acompound having a chromophoric group in the molecule.

In the case of azo dyestuffs, this can be accomplished by reacting aprimary aromatic amine with an appropriate amount of an alkylene oxideor mixtures of alkylene oxides, such as ethylene oxide and the like,according to known procedures, and then coupling the resulting compoundwith a diazonium salt of an aromatic amine.

In order to prepare liquid colorants of the triarylmethane class,aromatic amines that have been reacted as stated above with an alkyleneoxide are condensed with aromatic aldehydes and the resultingcondensation products oxidized to form the triarylmethane liquidcolorants.

Other suitable colorants can also be prepared by these and other knownprocedures. Colorants containing contaminating ionic species can be usedif purification methods are employed. Illustrative purification andchemical separation techniques include treatment with ion exchangeresins, reverse osmosis, extraction, absorption, distillation,filtration, and the like, and similar processes used to remove the ionicspecies and obtain a purified colorant that is electricallynon-conductive.

Non-limiting examples of commercially available non-conductive colorantsfor use in the heat transfer fluid include LIQUITINT Red ST or othersimilar polymeric colorants from Milliken Chemical of Spartanburg, S.C.,USA, or colorants from Chromatech of Canton, Mich., USA. Illustrativeexamples include the following: LIQUITINT Red ST, LIQUITINT Blue RE,LIQUITINT Red XC, LIQUITINT Patent Blue, LIQUITINT Bright Yellow,LIQUITINT Bright Orange, LIQUITINT Royal Blue, LIQUITINT Blue N-6,LIQUITINT Bright Blue, LIQUITINT Supra Blue, LIQUITINT Blue HP,LIQUITINT Blue DB, LIQUITINT Blue II, LIQUITINT Exp. Yellow 8614-6,LIQUITINT Yellow BL, LIQUITINT Yellow II, LIQUITINT Sunbeam Yellow,LIQUITINT Supra Yellow, LIQUITINT Green HMC, LIQUITINT violet, LIQUITINTRed BL, LIQUITINT Red RL, LIQUITINT Cherry Red, LIQUITINT Red II,LIQUITINT Teal, LIQUITINT Yellow LP, LIQUITINT Violet LS, LIQUITINTCrimson, LIQUITINT Aquamarine, LIQUITINT Green HMC, LIQUITINT Red HN,LIQUITINT Red ST, and combinations thereof.

In one exemplary embodiment, the non-conductive colorant is selectedfrom the group consisting of LIQUITINT Red ST from Milliken, LIQUITINTRed XC from Chromatech, CHROMATINT Yellow 1382 from Chromatech andLIQUITINT Blue® RE from Chromatech, while in an advantageous embodiment,the non-conductive colorant is LIQUITINT Blue RE from Chromatech.

The non-conductive colorant can be present in the heat transfer fluid inan amount of 0.0001 to 0.2 wt %, based on the total weight of the heattransfer fluid. In another embodiment, the non-conductive colorant canbe present in the heat transfer fluid in an amount of 0.0002 to 0.1 wt%, based on the total weight of the heat transfer fluid, while in oneexemplary embodiment, the non-conductive colorant can be present in anamount of 0.0003 to 0.05 wt %, based on the total weight of the heattransfer fluid.

The heat transfer fluids can also comprise additional additives such asother colorants, wetting agents, other antifoam agents, biocides,bitterants, nonionic dispersants or combinations thereof in amounts ofup to 10 wt %, based on the total weight of the heat transfer fluid.

The conductivity of the heat transfer fluid can be measured by using thetest methods described in ASTM D1125, that is, “Standard Test Methodsfor Electrical Conductivity and Resistivity of Water” or an equivalentmethod. The conductivity of the heat transfer fluid disclosed herein isless than about 100 μS/cm. In one embodiment, the conductivity is lessthan about 70 μS/cm, while in another embodiment, the conductivity isless than about 50 μS/cm, and yet in another embodiment the conductivityis less than about 25 μS/cm.

In other embodiments, the heat transfer fluid can have an electricalconductivity of about 0.02 to about 100 μS/cm, specifically about 0.02to about 50 μS/cm, more specifically about 0.05 to about 25 μS/cm, morespecifically about 0.05 to about 10 μS/cm. In one advantageousembodiment, the heat transfer fluid has an electrical conductivity ofabout 0.05 to about 5 μS/cm.

The heat transfer fluid can be prepared by mixing the differentcomponents together and homogenizing the resulting mixture. Generally,the alcohol and water are advantageously mixed together first. The othercomponents and additives are then added to the alcohol-water mixture bymixing and adequate stirring. In one embodiment, the alcohol is mixedwith the other components first, excluding the water. The resultingmixture is then homogenized. Water can then be added prior to packagingand/or prior to use of the heat transfer fluid.

The heat transfer fluid can be used in a variety of assemblies. It isadvantageous to use the heat transfer fluid in assemblies comprisingheat transfer systems which comprise aluminum and/or magnesium, andwherein the heat transfer fluid, once introduced into the heat transfersystem, is in contact with the aluminum and/or magnesium. It is alsoadvantageous to use the heat transfer fluid in assemblies where the heattransfer fluid is exposed to an electrical current (such as in fuelcells, and the like).

The assemblies comprise internal combustion engines or alternative powersources, among others. Internal combustion engines include those thatare powered by gasoline, and also those that are powered by natural gas,diesel, methanol, hydrogen, the condensation of steam, and/or the like.Non-limiting examples of alternative power sources include batteries,fuel cells, solar cells, solar panels, photovoltaic cells. Alternativepower sources can include devices powered by internal combustion enginesoperating with a clean heat transfer system, that is, a heat transfersystem that does not contribute to the concentration of ionic species inthe heat transfer fluid. Such alternative power sources can be usedalone or in combination, such as those employed in hybrid vehicles.

Assemblies comprising such alternative power sources include anyassembly that can traditionally be powered by an internal combustionengine, such as automotive vehicles, boats, generators, lights,aircrafts, airplanes, trains, locomotives, military transport vehicles,stationary engines, and the like. The assemblies also include additionalsystems or devices required for the proper utilization of power sources,such as electric motors, DC/DC converters, DC/AC inverters, electricgenerators, and other power electronic devices, and the like.

Other exemplary heat transfer systems wherein the heat transfer fluid isexposed to an electrical current include those that are used in glassand metal manufacturing processes where a high electricalvoltage/current is applied to the electrodes to keep a material such asglass or steel in a molten state. Such processes generally require aheat transfer fluid having low conductivity to cool the electrodes.

The disclosed assemblies include a power source comprising a heattransfer system in thermal communication with the alternative powersource and with the heat transfer fluid. In one embodiment, the heattransfer system comprises a circulation loop defining a flow path forthe heat transfer fluid. The heat transfer system can be integrated withthe power source, that is, the power source can be a part of the heattransfer system. In one embodiment, the heat transfer system comprises acirculation loop defining a flow path for the heat transfer fluid, thecirculation loop flowing through the power source.

Thus, in one embodiment, a heat transfer system comprises a circulationloop defining a flow path for a heat transfer fluid, and a heat transferfluid comprising a liquid coolant, a siloxane corrosion inhibitor, and anon-conductive polydiorganosiloxane antifoam agent, wherein theconductivity of the heat transfer fluid is less than about 100 μS/cm,and wherein the heat transfer system comprises aluminum, magnesium, or acombination thereof, in intimate contact with the heat transfer fluid.

In an exemplary embodiment referred to in FIG. 1, the power source is aninternal combustion engine, and the heat transfer system comprisesmagnesium. It will be understood that while FIG. 1 refers to anexemplary embodiment wherein the heat transfer system comprisesmagnesium, it is not limited thereto and can also comprise aluminum, orthe like. A combination of the metals can also be used.

Thus, referring now to FIG. 1, an exemplary heat transfer system 10comprises a heat transfer fluid reservoir 12, a pump 14, an engine 16, aheater core 18, a thermostat 20, a radiator cap 22, an overflow tank 26and a radiator 24. The heat transfer system can further comprise an ionexchange resin 28, conduits (e.g., pipe 30), valves (not shown) andother pumps. Each component of the heat transfer system 10 can comprisemagnesium. In one exemplary embodiment, at least one of the componentsof the heat transfer system 10 comprises magnesium and/or magnesiumalloys. In another exemplary embodiment, each of the pump 14, the engine16, the heater core 18, the thermostat 20, the radiator cap 22, theoverflow tank 26, and the radiator 24 comprises magnesium. In anotherexemplary embodiment, one or more components comprise magnesium whileone or more other components comprise aluminum.

The reservoir 12 is provided to maintain the heat transfer fluid in anenvironment free from undesirable contaminants when the fluid is notcirculating. In one embodiment, reservoir 12 comprises plastic.

The pump 14 is provided to drive the fluid through the heat transfersystem 10. Specifically, pump 14 routes fluid from the reservoir,through an engine block of the engine 16, that is, through a first setof interior passages of the engine that are disposed proximate theengine cylinder, through heater core 18, through a second set ofinterior passages of the engine block, and to the thermostat 20.Depending on the position of the thermostat 20, the fluid is then routedthrough either the radiator cap 22, the radiator 24, then to the pump14, or directly to the pump 14. The pump 14 can be a centrifugal pumpdriven by a belt connected to a crankshaft of the engine 16. The pump 14pumps heat transfer fluid through the heat transfer system 10 when theengine 16 is operating. The pump 14 can comprise a rotating componentcomprising an impeller and a shaft. The pump 14 can further comprise astationary component comprising a casing, a casing cover, and bearings.In an exemplary embodiment both the rotating component of the pump andthe casing component of the pump comprise magnesium. In anotherexemplary embodiment only the rotating component, the casing component,or subcomponents of the rotating component and casing component comprisemagnesium.

The engine 16 comprises the engine block, cylinders, cylinder connectingrods, and a crankshaft. The engine block comprises internal passagewaysdisposed therethrough. The internal passageway can be cast or machinedin the engine block. The heat transfer fluid can be routed through theinternal passageways of the engine to transfer heat from the engine.These passageways direct the heat transfer so that the fluid cantransfer heat away from the engine to optimize engine performance.

In an exemplary embodiment the metal engine components comprisemagnesium. Specifically, the engine block, the cylinders, the cylinderconnecting rods, and the crankshaft comprise magnesium. In analternative exemplary embodiment, certain engine components can comprisemagnesium, while other engine components do not comprise magnesium. Forexample, the engine block can comprise magnesium, while the cylinder,cylinder connecting rods, and the crankshaft can comprise steel.

The heater core 18 is provided to cool the heat transfer fluid whileheating a vehicle interior. The heater core 18 can comprise a series ofthin flattened tubes having a high interior surface area and exteriorsurface area such that heat can be effectively transferred away from theheat transfer fluid. In an exemplary embodiment, the heating core 18comprises magnesium tubes brazed together. In another exemplaryembodiment the heating core can comprise tubes joined together by otherjoining methods or the heating core can be cast as a single unit. Aircan be forced past the heater core to increase the cooling rate of theheat transfer fluid.

The thermostat 20 is provided to measure a temperature indicative of aselected heat transfer fluid temperature and selectively routes the heattransfer fluid to the radiator or to the pump. Thermostat 20 routes theheat transfer fluid to the radiator when the temperature of the heattransfer fluid is greater than or equal to the selected temperature andto the pump when the temperature of the heat transfer fluid is less thanthe selected temperature. The thermostat has an inlet portion, aradiator outlet portion, a radiator bypass outlet portion, and a valveportion. A single housing member can define the inlet portion, theradiator outlet portion, and the radiator bypass outlet portion. Thevalve portion can be disposed within the single housing member andprovide selective communication between the inlet portion and both theradiator outlet portion and the radiator bypass outlet portion. When thevalve is in a closed position, the thermostat routes the heat transferfluid directly to the pump. When the valve is in the open position, thethermostat routes the heat transfer fluid through the radiator. In anexemplary embodiment, the thermostat valve portion and the thermostathousing member comprise magnesium. In another exemplary embodiment, onlythe housing or only the valve portion comprise magnesium.

The radiator cap 22 is provided to seal the heat transfer system and tomaintain the heat transfer fluid at a selected pressure to prevent theheat transfer fluid from boiling. In an exemplary embodiment, theradiator cap 22 comprises magnesium.

The radiator 24 is provided to cool the heat transfer fluid. Theradiator 24 can comprise a series of thin flattened tubes having a highinterior surface area and exterior surface area such that heat can beeffectively transferred from the heat transfer fluid. In an exemplaryembodiment, the radiator 24 comprises magnesium tubes brazed together.In another exemplary embodiment the radiator can comprise tubes joinedtogether by other joining methods or case as a single unit. Air can beforced past the radiator to increasing the cooling rate of the heattransfer fluid.

The optional ion exchange resin (not shown) exchanges ions with the heattransfer fluid. Specifically, the ion exchange resin removes corrosiveions from the heat transfer fluid and replaces the corrosive ions withions that reduce the caustic properties of the heat transfer fluid. Theion exchange resin is in fluid communication with the heat transferfluid, and with the flow path and/or circulation loop defined by theheat transfer system. In one embodiment, the heat transfer system 10comprises an ion exchange resin. In one embodiment, the ion exchangeresin is disposed between the engine and the thermostat.

In another embodiment, the ion exchange resin is disposed in otherlocations of the heat transfer system 10. For example, the ion exchangeresin is disposed between other heat transfer system components.Further, the ion exchange resin can be disposed within the heat transfersystem components, such as in the heat transfer fluid reservoir.

Non-limiting examples of ion exchange resins include anion exchangeresins, cation exchange resins, mixed bed ion exchange resins, andcombinations thereof. The ion exchange resin comprises a polymer matrixcomprising polymers comprising functional groups paired with anexchangeable ion. The exchangeable ion is generally one or more of Na+,H+, OH−, or Cl− ions, depending on the type of ion exchange resin.

Non-limiting examples of polymers comprised in the polymer matrixinclude polystyrene, polystyrene and styrene copolymers, polyacrylates,aromatic substituted vinyl copolymers, polymethacrylates,phenol-formaldehyde, polyalkylamine, and the like, and combinationsthereof. In one embodiment, the polymer matrix comprises polystyrene andstyrene copolymers, polyacrylates, or polymethacrylates, while in oneexemplary embodiment, the polymer matrix comprises styrenedivinylbenzenecopolymers.

Non-limiting examples of functional groups in cation ion exchange resinsinclude sulfonic acid groups (—SO3H), phosphonic acid groups (—PO3H),phosphinic acid groups (—PO2H), carboxylic acid groups (—COOH or—C(CH3)-COOH), and the like, and combinations thereof. In oneembodiment, the functional groups in the cation exchange resin are—SO3H, —PO3H, or —COOH, while in one exemplary embodiment, thefunctional groups in the cation exchange resin are —SO3H.

Non-limiting examples of functional groups in anion exchange resinsinclude quaternary ammonium groups such as benzyltrimethylammoniumgroups, termed type 1 resins, benzyldimethylethanolammonium groups,termed type 2 resins, trialkylbenzyl ammonium groups, also termed type 1resins, tertiary amine functional groups, and the like. In oneembodiment, the functional groups in the anion exchange resin arebenzyltrimethylammonium, or dimethyl-2-hydroxyethylbenzyl ammonium,while in one exemplary embodiment the functional groups in the anionexchange resin are benzyltrimethylammonium.

The particular ion exchange resin selected is dependent upon thecomposition of the heat transfer fluid, and can exchange ions with anyionic species produced by the heat transfer fluid. For example, if thesiloxane corrosion inhibitor, the non-conductive polydimethylsiloxaneantifoam agent, the azole, or any additive in the heat transfer fluidare more likely to become negatively charged, the ion exchange resinshould be a mixed bed resin, an anion exchange resin, or a combinationthereof. Commercially available anion exchange resins typically compriseOH− or Cl− exchangeable ions. In one embodiment, the exchangeable ion isOH−.

Alternatively, if the siloxane corrosion inhibitor, the non-conductivepolydimethylsiloxane antifoam agent, the azole, or any additive in theheat transfer fluid are likely to become positively charged, then mixedbed resins, cation exchange resins or a combination thereof should beused. Commercially available cation exchange resins typically compriseH+ or Na+ exchangeable ions. In one embodiment, the exchangeable ion isH+.

Commercially available ion exchange resins suitable for use herein areavailable from Rohm & Haas of Philadelphia, Pa. as AMBERLITE, AMBERJET,DUOLITE, and IMAC resins, from Bayer of Leverkusen, Germany as LEWATITresin, from Dow Chemical of Midland, Mich. as DOWEX resin, fromMitsubishi Chemical of Tokyo, Japan as DIAION and RELITE resins, fromPurolite of Bala Cynwyd, Pa. as PUROLITE resin, from Sybron ofBirmingham, N.J. as IONAC resin, from Resintech of West Berlin, N.J.,and the like. In one embodiment, the suitable commercially available ionexchange resin is DOWEX MR-3 LC NG Mix mixed bed resin, DOWEX MR-450 UPWmixed bed resin, IONEC NM-60 mixed bed resin, or AMBERLITE MB-150 mixedbed resin, while in one exemplary embodiment, the suitable commerciallyavailable ion exchange resin is DOWEX MR-3 LC NG Mix.

In one embodiment, the ion exchange resin is pre-treated with acorrosion inhibiting composition prior to use in the heat transfersystem. The ion exchange resin is pre-treated by contacting the ionexchange resins with an aqueous corrosion inhibiting solution comprisingthe corrosion inhibiting composition for a selected time period. In oneembodiment, the ion exchange resin is contacted with the aqueouscorrosion inhibiting composition solution for a period of timesufficient to allow the corrosion inhibiting composition to exchangeions with at least about 15% of the total exchangeable ions, based onthe total number of exchangeable ions in the ion exchange resin. Thatis, the corrosion inhibiting composition loading of the corrosioninhibiting composition treated ion exchange resin should be at leastabout 15% of the exchange capacity of the ion exchange resin. In anotherembodiment, the period of contact is sufficient to allow the corrosioninhibiting compositions to exchange ions with at least about 50% of thetotal exchangeable ions, based on the total number of exchangeable ionsin the ion exchange resin. In one exemplary embodiment, the period ofcontact is sufficient to allow the corrosion inhibiting composition toexchange ions with at least about 75% of the total exchangeable ions,based on the total number of exchangeable ions in the ion exchangeresin. In another exemplary embodiment, the period of contact issufficient to allow the corrosion inhibiting composition loading of thecorrosion inhibiting composition treated ion exchange resin to be anamount of about 15 to about 99% of the total exchange capacity of theion exchange resin or from about 15 to about 99% of the totalexchangeable ions, based on the total number of exchangeable ions in theion exchange resin.

In one exemplary embodiment, the resultant corrosion inhibitingcomposition treated ion exchange resins will be cleansed with de-ionizedwater and/or the heat transfer fluid to minimize the chance foraccidental introduction of impurities.

In one embodiment, ion exchange resins in Na+ or Cl− forms are used onlyif the treatment with the aqueous corrosion inhibiting solution resultsin the removal of substantially all of the Na+ or Cl− ions from the ionexchange resin. In one embodiment, ion exchange resins in Na+ or Cl−forms are used if the treatment with the aqueous corrosion inhibitingsolution results in the corrosion inhibiting composition loading of thecorrosion inhibiting composition treated ion exchange resin being atleast about 80% of the total exchangeable ions.

The corrosion inhibiting compositions for treating the ion exchangeresin comprises a siloxane corrosion inhibitor, an azole, or acombination thereof. Suitable siloxane corrosion inhibitors and azolesare those described above. The corrosion inhibiting compositions areweakly ionic and therefore, when in contact with the heat transferfluid, maintain the low conductivity of the heat transfer fluid.

The amount of corrosion inhibiting composition released from the resindepends on the level of corrosive ions in the heat transfer fluid. Thecorrosion inhibiting composition is advantageous since an increase inthe amount of corrosive ions in the heat transfer fluid produces anincrease in the amount of corrosion inhibiting composition from theresin being released into the heat transfer fluid due to the ionexchange mechanism. The increase in the amount of corrosion inhibitingcomposition concentration in the heat transfer fluid will lead to areduction in the corrosion rate. Another advantage of the heat transfersystem is that the presence of the ion exchange rein, andadvantageously, the mixed bed ion exchange resin, will also maintain lowconductivity in the heat transfer fluids in the system.

In one embodiment, acidic aqueous corrosion inhibiting solutionssuitable for treating the ion exchange resin have a pKa value of equalto or greater than about 5 at 25° C., specifically from about 5 to about14. In another embodiment, basic aqueous corrosion inhibiting solutionssuitable for treating the ion exchange resin have a pKb value of equalto or greater than about 5 at 25° C., specifically from about 5 to about14.

Further, the ion exchange resin can be treated with other additives suchas colorants, wetting agents, antifoam agents, biocides, and nonionicdispersants, with the proviso that the other additives do notsubstantially increase the overall electrical conductivity of the heattransfer fluid when the additives are added to the heat transfer fluid.

In one embodiment, the ion exchange resin will be treated with anon-conductive polydimethylsiloxane emulsion based antifoam. Suitablepolydimethylsiloxane emulsion based antifoams include those describedabove.

In another exemplary embodiment referred to in FIG. 2, an assemblycomprises a power source that can be an internal combustion engine, oradvantageously, an alternative power source, specifically a solar cellor fuel cell. The heat transfer system comprises magnesium. The assemblycan also comprise a regenerative braking system. It will be understoodthat while FIG. 2 refers to an exemplary embodiment wherein the heattransfer system comprises magnesium or aluminum, any other susceptiblemetal can be used therein.

Thus, referring now to FIG. 2, an exemplary heat transfer system 116comprises an internal combustion engine 105, or fuel cells 105 or solarcells 105 as the primary power source 107. It also comprises arechargeable secondary battery 112 or an optional ultra-capacitor 113that can be charged via the assembly's regenerative braking system. Thebattery 112 and/or the ultra-capacitor 113 can act as secondary powersources. The assembly can further comprise power electronic devices,such as DC/DC converters 110, DC/AC inverters 110, generators 108, powersplitting devices 109, and/or voltage boost converters 111, and thelike. In addition, the assembly can contain fuel cell or solar cell“balance of plant” subsystems 106. These can be air compressors, pumps,power regulators, and the like. The assembly also comprises HAVC systems114, such as, air-conditioning system for the climate control ofassembly interior space. The heat transfer system 116 further comprisesa pump 101, heat transfer fluid flow path 104, heat transfer fluid tank102, and a radiator or heat exchanger 103, and a fan 115. The fan can besubstituted by an external cooling source, such as a different (orisolated) cooling system with its own cooling media. An ion exchangeresin (not shown) can also be present, and is as described above.

In one embodiment, the alternative power source is a fuel cell. The fuelcell is in thermal communication with the heat transfer systems andfluids. In one embodiment, the electrical conductivity of the heattransfer fluids is less than about 10 μS/cm. In an exemplary embodimentcomprising a fuel cell, the heat transfer fluid comprises an electricalconductivity of about 0.02 to about 10 μS/cm. In one advantageousembodiment, the heat transfer fluid comprises an electrical conductivityof about 0.05 to about 5 μS/cm.

The heat transfer fluid can be used in a number of different types offuel cells comprising an electrode assembly comprising an anode, acathode, and an electrolyte, and a heat transfer fluid in thermalcommunication with the electrode assembly or fuel cell. In oneembodiment the heat transfer fluid can be contained or flow in channelor flow path defined by a circulation loop or heat transfer fluid flowchannel in thermal communication with the fuel cell.

Non-limiting examples of fuel cells include PEM (Proton ExchangeMembrane or Polymer Electrolyte Membrane) fuel cells, AFC (alkaline fuelcell), PAFC (phosphoric acid fuel cell), MCFC (molten carbonate fuelcell), SOFC (solid oxide fuel cell), and the like. In one exemplaryembodiment, the heat transfer fluid is used in PEM and AFC fuel cells.

The invention is further illustrated by the following non-limitingexamples.

Examples 1-14

Table 1 illustrates the composition of heat transfer fluids, representedby Fn, with n being the number of the fluid.

TABLE 1 Fluid (Fn) Composition F1 50 wt % conventional coolantcomprising ionic corrosion inhibitors. The concentrate of this coolantcontains greater than 94 wt % ethylene glycol, 0.1 to 0.3 wt %tolyltriazole, 0.2 to 0.5 wt % nitrate, up to 0.1 wt % molybdate, 0.1 to2.0 wt % borax, 0.1 to 0.5 wt % phosphoric acid, 0.1 to 0.5 wt % ofsilicate, 0.4 to 2.0 wt % of NaOH or KOH or their mixtures, very smallamounts (e.g., less than 0.1 wt %) of antifoams and colorants. F2 50 wt% monoethylene glycol, 0.116 wt % siloxane corrosion inhibitor (i.e.,Silwet L-7657 from GE Silicone; 116 ppm benzotriazole, 350 ppmnon-conductive polydimethylsiloxane antifoam agent (i.e., PC-5450 NFantifoam), the balance deionized water. F3 50 wt % monoethylene glycol,the balance deionized water. F4 43 wt % mixture of ethylene glycol and1,2-propylene glycol (~80 wt % of the mixture is ethylene glycol and theremaining ~20 wt % is 1,2-propylene glycol), 400 ppm siloxane corrosioninhibitor, or Silwet L-7657, 100 ppm benzotriazole, 800 ppmnon-conductive polydimethylsiloxane antifoam agent, or PC-5450 NFantifoam, the balance deionized water. F5 50 wt % monoethylene glycol,400 ppm siloxane based corrosion inhibitor Silwet L-7657; 100 ppmbenzotriazole, 800 ppm non-conductive polydimethylsiloxane antifoamagent PC-5450 NF, the balance deionized water. F6 50 wt % monoethyleneglycol, 400 ppm siloxane corrosion inhibitor Silwet L-7657, 100 ppmbenzotriazole, 800 ppm non-conductive polydimethylsiloxane antifoamagent, i.e., PC-5450 NF, 100 ppm sorbitan fatty acid esters, i.e., Span20, available from Aldrich, 100 ppm polyethylene glycol corrosioninhibiting surfactant, i.e., Carbowax 400, available from from DowChemicals, the balance deionized water. F7 50 volume % (vol %) ValvolineZEREX G-05 (hybrid) coolant, the balance deionized water. ValvolineZerex G-05 coolant concentrate contains greater than 94 wt % ethyleneglycol, 0.1 to 0.4 wt % nitrate, 0.1 to 0.4 wt % nitrite, 0.5 to 2.5 wt% borax, 0.05 to 0.15 wt % benzotriazole, 0.1 to 0.2 wt % silicate, 1 to3 wt % benzole acid, 0.4 to 2.0 wt % NaOH or KOH or their mixture, andvery small amounts (e.g., less than 0.1 wt %) of antifoams and colorantsand up to 0.5 wt % of a polymer dispersant. F8 50 vol % Toyota LONG LIFEred coolant, the balance deionized water. The coolant concentratecontains greater than 94 wt % ethylene glycol, 3 to 5 wt % benzole acid,0.1 to 0.3 wt % benzotriazole, 0.1 to 0.4 wt % mecaptobenzothiazole, 0.5to 1 wt % phosphoric acid, 0.5 to 1 wt % molybdate, 0.1 to 0.5 wt %nitrate, 0.5-5 wt % NaOH or KOH or their mixtures, and very smallamounts (e.g., less than 0.1 wt %) of antifoams and colorants, as wellas very small amount of other coolant additives such as a phosphonatescale inhibitor and hardness ions. F9 50 volume % Texaco HD coolant, thebalance deionized water. The coolant concentrate contains greater than94 wt % ethylene glycol, 2 to 4 wt % ethyl hexanoic acid, 0.1 to 0.4 wt% sebacic acid, 0.2 to 0.5 wt % tolytriazole, 0.1 to 0.4 wt % sodiumnitrite, 0.2 to 1 wt % molybdate, 0.5 to 5 wt % of KOH or NaOH or theirmixtures, and very small amounts (e.g., less than 0.1 wt %) ofantifoams, and colorants. F10 50 wt % monoethylene glycol, 400 ppmsiloxane based surfactant (i.e., Silwet L-7657), 100 ppm benzotriazole,800 ppm polydimethylsiloxane emulsion based antifoam (i.e., PC-5450 NF),200 ppm sorbitan fatty acid esters (i.e., Span-20), and 200 ppmpolyethylene glycol corrosion inhibiting surfactant (i.e., Carbowax400).

Table 2 illustrates the corrosion results obtained in a galvanic couplewhere a MRI202S magnesium alloy anode is galvanically coupled to acopper cathode. A 0.5 square centimeter magnesium alloy coupon is placedin a heat transfer fluid along with a 1.1 square centimeter copper alloycoupon. The coupons are placed 1 centimeter apart and the temperature ismaintained at 88° C. Conductivity, average corrosion rate, and corrosionloss level results of the magnesium alloys in solution are listed below.In each example magnesium corrosion loss was measured over a total timeof 12,000 seconds. En refers to Example, wherein n is the number of theexample.

The test solutions used are described in Table 1. In the galvanic coupleexperiment, the galvanic couple current density is measured as afunction of time. In general, the current density is varied over time.The total charge in Table 2 represents the total amount of the galvaniccorrosion occurring during a test. Average corrosion rate and corrosionloss data are calculated by using the total charge and total time of thetest according to the Faraday law and expected corrosion anodicreaction, i.e., Mg→Mg2++2e−.

Final galvanic couple current density represents the instant galvaniccorrosion rate of the magnesium alloy at the end of the test. Ingeneral, if the average corrosion rate and the corrosion loss value islower for a given inhibitive coolant formulation, it indicates that thecoolant formulation is providing a better corrosion protection than acoolant formulation that yields a higher corrosion rate.

In Examples 3-8 an ion exchange resin is also placed in the solution.Resin 1 comprises 3 grams of DOWEX MR-450 UPW. Resin 2 comprises 3.5grams of Amberjet UP6040 ion exchange resin, treated with an aqueousbenzotriazole solution. Resin 3 comprises 7.0 grams of DOWEX MR-450 UPWand 1.75 grams of untreated Amberjet UP6040. Resin 4 comprises 7.0 gramsof DOWEX MR-450 UPW treated with an aqueous benzotriazole solution.Resin 5 comprises 14.35 grams of Dowex MR-450 UPW treated with anaqueous benzotriazole solution and 3.5 grams of untreated DOWEX MR-450UPW. The dry resin is the resin refers to the resin as received from thesupplier. The wet resin refers to the resin treated with an aqueousbenzotriazole solution. The resin after treatment was recovered from thetreatment container, i.e., a pyrex beaker, using a stainless steelspatula. The resin was then transferred to a clean and inert ionexchange resin filter bag made of Nylon. The excess amount of water wasdrained by the force of gravity. After the excess amount of water wasremoved from the treated resin, the resin was stored in a clean glassbottle for later use. The benzotriazole pretreatment of the resin wastypically conducted by adding 10 g of Dowex MR-450 UPW mixed bed ionexchange resin into 1 liter of deionized water. Before adding the ionexchange resin, 1200 mg/L benzotriazole was dissolved in the 1 liter ofthe deionized water. Under constant magnetic stirring via the use of aTeflon coated magnet stirring bar and a magnetic stirrer, the resin andthe benzotriazole aqueous solution were allowed to react for 22 hours atroom temperature. During this treatment process, benzotriazole isexchanged with H+ and OH− groups in the mixed bed ion exchange resin sothat the resin is saturated with benzotriazole at all the exchangeablesites. The mixed bed ion exchange resin obtained after the treatment istermed the benzotriazole treated resin.

TABLE 2 Example (En) E1 E2 E3 E4 E5 E6 E7 E8 Fluid (Fn) F1 F2 F2 F2 F2F3 F4 F5 Ion Exchange Resin None None Resin 1 Resin 2 Resin 3 Resin 1Resin 4 Resin 5 Total Charge (mC/cm²) 3704 237.6 16.44 56.86 18.72 14.8772.45 24.73 Final Current Density at 210.8 25.51 1.226 4.238 1.432 1.0735.827 1.884 the end of the galvanic couple test (μA/cm²) Averagecorrosion Rate 19.322 1.239 0.086 0.291 0.098 0.078 0.378 0.129 (μm/day)Corrosion Loss 23.508 1.508 0.104 0.355 0.119 0.094 0.460 0.157(mg/week/cm²) Conductivity N.D. 1.09/4.97 1.16/0.16 0.78/N.D. 0.14/0.150.29/0.19 0.29/0.41 0.98/0.17 Initial/Final (μS/cm) Final BZT (ppm) N.D.N.D. 0 N.D. 12 0 157 27 N.D. = not detectable

Table 3 illustrates the test results obtained in galvanic couplecorrosion experiments where a MRI202S magnesium alloy anode isgalvanically coupled to a mild steel C1018 cathode. A 0.5 squarecentimeter magnesium alloy coupon is placed in a heat transfer fluidalong with a 1.1 square centimeter steel coupon. The coupons are placed1 centimeter apart and the temperature is maintained at 88° C.Conductivity, average corrosion rate, and corrosion loss level resultsof the magnesium alloys in solution are listed below. In each examplemagnesium corrosion loss was measured over a total time of 12,000seconds.

In Examples 9 and 14 an ion exchange resin is also placed in thesolution. Resin 6 comprises 10 grams of MR-450 UPW treated with anaqueous benzotriazole solution and 3 grams of MR-450UPW. Resin 7comprises 10 grams of MR-450 UPW treated with an aqueous benzotriazolesolution and 3.7 grams of MR-450UPW.

TABLE 3 Example (En) E9 E10 E11 E12 E13 E14 Fluid (Fn) F6 F7 F8 F1 F9F10 Ion Exchange Resin Resin 6 None None None None Resin 7 Total Charge(mC/cm²) 40.3 41210 513.1 58.34 13280 19.26 Current Density (μA/cm²)3.32 2640 35.84 3.657 982.1 1.33 Total Time (sec) 1200 1200 11333 12001200 1200 Av corr Rate (μm/day) 0.210 214.977 2.834 0.304 69.277 0.100Corr Loss (mg/week/cm²) 0.256 261.542 3.448 0.370 84.284 0.122Conductivity 1.03/0.20 6770/6110 10550/9230 3510/2890 6970/60201.05/0.14 Initial/Final (μS/cm) Final BZT (ppm) 39 N.D. N.D. N.D. N.D.N.D.

As can be seen from Tables 2 and 3, the heat transfer fluids lacking thesiloxane corrosion inhibitor and non-conductive polydimethylsiloxaneantifoam agent has an average corrosion loss rate of greater than 0.3and up to as high as about 215 μm/day for E10. The examples with asiloxane corrosion inhibitor, an azole and a non-conductivepolydimethylsiloxane antifoam agent have a magnesium average corrosionloss rates of less than 2.1 μm/day. It can also be seen that thebenzotriazole-treated ion exchange resins can be used to keep theconductivity similar to when untreated ion exchange resins are used, andthe same time allow the presence of benzotriazole residual concentrationin the heat transfer fluid to provide the desirable corrosion protectionfor copper based alloys and other metals in the heat transfer system.

Example 15-26

Tables 5 and 6 illustrate the test results obtained in galvanic couplecorrosion tests where galvanic couples C1-C5 of Table 4 were used. Thesegalvanic couples are exemplary magnesium-based compositions for use inautomotive magnesium-based heat transfer systems, among others. The massloss was determined according to a modified ASTM-D1384 procedure. TheASTM-D1384 test was modified by using different arrangement of metalcoupons as described in Table 4.

TABLE 4 C1 Mg AS-21x (coupled to Brass via an AI 6061 spacer) C2 MgAS-21x (coupled to SAE329 cast AI via an AI 6061 spacer) C3 CastAluminum SAE329 (coupled to Mg via AI 6061 spacer) C4 Aluminum 3003 C5Mg AS-21x

TABLE 5 Example (En) E15 E16 E17 E18 E19 E20 Couple used (Cn) C1 C2 C3C4 C5 C6 Mass Loss 2.5 34.1 22.2 −1.7* 0.8 16.8 (mg/cm²/week) Total MassLoss 0.046 0.573 0.373 −0.029* 0.015 0.282 (mg/sample) Heat TransferFluid 60 wt % monoethylene glycol, 250 mg/L benzotriazole, and 0.1 wt %anthranilamide. *Indicates a mass gain

TABLE 6 Example (En) E21 E22 E23 E24 E25 E26 Composition (Cn) C1 C2 C3C4 C5 C6 Mass Loss 0.6 19.1 19.0 −0.6* 0.5 8.6 (mg/cm²/week) Total MassLoss 0.011 0.321 0.319 −0.010* 0.009 0.144 (mg/sample) Heat TransferFluid 60 wt % monoethylene glycol, 400 mg/L SILWET L-7657, 800 mg/Lnon-conductive polydimethylsiloxane antifoam agent, 100 mg/Lbenzotriazole. *Indicates a mass gain

As can be seen from Tables 5 and 6, the metals galvanically coupledthrough heat transfer fluids that comprise a siloxane corrosioninhibitor, and a non-conductive polydimethylsiloxane antifoam agent(Table 6) exhibit substantially less weight loss due to corrosion thanmetals galvanically coupled through heat transfer fluids which lack thesiloxane corrosion inhibitor, and a non-conductive polydimethylsiloxaneantifoam agent (Table 5).

Example 27-34

The following examples illustrate the ability of the ion exchange resinsto reduce the conductivity of a heat transfer fluid.

Table 7 illustrates the results for Examples 27 and 28.10 g of the resinwas first immersed in 1000 g of a 50 wt % ethylene glycol aqueoussolution comprising 1200 ppm benzotriazole, and stirred for 22 hours. 1g of the resulting pretreated resin was then immersed in 100 g of a50:50 ethyleneglycol:deionized water solution comprising 30 ppm sodiumformate and 30 ppm sodium acetate and stirred. Example 27 comprises aUP6040 resin and Example 28 comprises a DOWEX MR-3 LC NG Mix resin.

TABLE 7 Conductivity (μS/cm) Time (min) E27 E28 0 25.8 25.9 20 16.1816.98 40 9.13 10.76 60 5.87 7.33 103 2.21 3.22 150 0.72 1.17 200 0.450.57 235 0.39 0.47

Table 8 illustrates the results for Example 29. 9.7 g of the resin wasfirst immersed in 1000 g of a 50 wt % ethylene glycol aqueous solutioncomprising 1300 ppm tolyltriazole, and stirred for 22 hours. 1 g of theresulting pretreated resin was then immersed in 100 g of a 50:50ethyleneglycol:deionized water solution comprising 30 ppm sodium formateand 30 ppm sodium acetate and stirred. Example 29 comprises a DOWEX MR-3LC NG Mix Resin.

TABLE 8 Conductivity (μS/cm) Time (min) E29 0 28.3 20 18.32 40 12.39 607.59 90 5.31 120 3.11 150 1.87 220 0.85 240 0.55

Table 9 illustrates the results for Examples 30-32. Example 30 was ablank resin conductivity test. In Example 29, 10 g of MTO-DOWEX MR-3 LCNG Mix resin were pretreated by immersing in 250 g of a 50 wt % ethyleneglycol aqueous solution comprising 1200 ppm benzotriazole. In Example30, 10 g of MTO-DOWEX MR-3 LC NG Mix resin were pretreated by immersingin 500 g of a 50 wt % ethylene glycol aqueous solution comprising 1200ppm benzotriazole. 1 g of the treated resin was immersed in 100 g of a50 wt % ethylene glycol solution comprising 30 ppm NaCl and stirred.

TABLE 9 E30 E31 E32 Time Conductivity Time Conductivity TimeConductivity (min) (μS/cm) (min) (μS/cm) (min) (μS/cm) 0 36.9 0 37.3 038.2 20 25.9 20 22.2 20 26.6 40 15.37 45 9.18 40 16.6 60 8.99 56 6.57 657.77 80 4.84 75 3.15 85 5.09 105 2.19 130 0.61 105 2.81 127 1.09 1810.15 120 2 180 0.18 200 0.11 140 1.3 240 0.08 240 0.08 190 0.38 240 0.16

Table 10 illustrates the results for Examples 33-35. For Example 33, 10g of MTO-DOWEX MR-3 LC NG Mix resin were pretreated by immersing in 750g of a 50 wt % ethylene glycol aqueous solution comprising 1200 ppmbenzotriazole. For Example 234, 10 g of MTO-DOWEX MR-3 LC NG Mix resinwere pretreated by immersing in 1000 g of a 50 wt % ethylene glycolaqueous solution comprising 1200 ppm benzotriazole. For Example 35, 10 gof MTO-DOWEX MR-3 LC NG Mix resin were pretreated by immersing in 1000 gof a 50 wt % ethylene glycol aqueous solution comprising 1300 ppmtolyltriazole. 1 g of the treated resin was immersed in 100 g of a 50 wt% ethylene glycol solution comprising 30 ppm NaCl and stirred.

TABLE 10 E33 E34 E35 Conductivity Time Conductivity Time ConductivityTime (min) (μS/cm) (min) (μS/cm) (min) (μS/cm) 0 35.8 0 39.4 0 38.7 2020.0 25 17.09 20 25.1 40 12.42 45 11.1 40 18.16 60 8.77 80 4.39 60 10.89103 2.95 105 2.21 90 6.80 150 0.68 130 1.24 120 3.10 200 0.25 160 0.59150 1.53 235 0.20 185 0.4 220 0.55 215 0.33 240 0.34 236 0.31 Residual14 ppm 102 ppm 130 ppm benzotriazole

It can be seen from the data in Tables 7-10 that benzotriazole andtolyltriazole treated resins are effective at removing undesirable ionicimpurities such as Na+, Cl−, formate, and acetate and thus reducing theconductivity of the thermal exchange fluid while keeping theconductivity at a low level. The benzotriazole or tolyltriazole treatedion exchange resin can also leave a desirable residual amount of thetriazole in the heat transfer fluid as can be seen in Examples 33-35,and thus maintaining effective corrosion protection for metals in theheat transfer system.

This written description uses examples and figures to disclose theinvention, including the best mode, and also to enable any personskilled in the art to make and use the invention. The patentable scopeof the invention is defined by the claims, and can include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal language of the claims.

All cited patents, patent applications, and other references areincorporated herein by reference in their entirety unless otherwiseindicated. However, if a term in the present application contradicts orconflicts with a term in the incorporated reference, the term from thepresent application takes precedence over the conflicting term from theincorporated reference.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other. Further,disclosing a range is specifically disclosing all ranges formed from anypair of any upper range limit and any lower range limit within thisrange, regardless of whether ranges are separately disclosed. It is notintended that the scope of the invention be limited to the specificvalues recited when defining a range.

The use of the terms “a”, “an”, “the”, and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Further, it should be noted that the terms “first,” “second,”and the like herein do not denote any order, quantity, or importance,but rather are used to distinguish one element from another.

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (e.g., itincludes the degree of error associated with measurement of theparticular quantity).

Certain compounds are described herein using a general formula thatincludes variables such as, but not limited to, R1, R2, R3, X, Y, andthe like. Unless otherwise specified, each variable within such aformula is defined independently of other variables.

The term “substituted” as used herein means that any one or morehydrogen atoms on the designated atom or group is replaced with aselection from the indicated group, provided that the designated atom'snormal valence is not exceeded.

As used herein, the term “alkyl” includes both branched and straightchain saturated aliphatic hydrocarbon groups, having the specifiednumber of carbon atoms. The term C1-C7 alkyl as used herein indicates analkyl group having from 1 to about 7 carbon atoms. When C0-Cp alkyl isused herein in conjunction with another group, for example,heterocycloalkyl (C0-C2 alkyl), the indicated group, in this caseheterocycloalkyl, is either directly bound by a single covalent bond(C0), or attached by an alkyl chain having the specified number ofcarbon atoms, in this case from 1 to p carbon atoms. Examples of alkylinclude, but are not limited to, methyl, ethyl, n-propyl, isopropyl,n-butyl, 3-methylbutyl, t-butyl, n-pentyl, and sec-pentyl.

The term “non-conductive” as used herein relates to a species thatproduces a conductivity increase of less than about 10 μS/cm whenintroduced into a standard solution of deionized water, at a maximumconcentration of no more than 0.2% by weight, based on the total weightof the standard solution.

“Substantially free of” as used herein refers to an amount that is notin excess of an amount that will lead to the conductivity of the heattransfer fluid to increase by more than 10 μS/cm.

“Alternative power sources” as used herein refers to power sourcetechnologies that provide improvements in energy efficiency,environmental concerns, waste production, and management issues, naturalresource management, and the like.

“Metal” as used herein refers to the element metal, wherein “metalalloy” or “metallic alloy” refers to the metal in combination with oneor more other metals. For example, magnesium refers to the elementmagnesium, whereas a magnesium alloy refers to a combination ofmagnesium with one or more other metals. Thus, a magnesium alloycomprises magnesium, and a system comprising magnesium can compriseeither elemental magnesium alone, a magnesium alloy, or a combination ofelemental magnesium and a magnesium alloy.

“High conductivity” as used herein refers to a conductivity of greaterthan 100 □S/cm.

1. A heat transfer system, comprising: a circulation loop defining aflow path for a heat transfer fluid; and a heat transfer fluid,comprising: a liquid coolant; a siloxane corrosion inhibitor of formulaR₃—Si—[O—Si(R)₂]_(x)—OSiR₃, wherein R is independently an alkyl group ora polyalkylene oxide copolymer of 1 to 200 carbons, x is from 0 to 100,and further wherein at least one alkyl group and at least onepolyalkylene oxide copolymer are present; and a non-conductivepolydiorganosiloxane antifoam agent; wherein the conductivity of theheat transfer fluid is less than about 100 μS/cm; and wherein the heattransfer system comprises aluminum, magnesium, or a combination thereof,in intimate contact with the heat transfer fluid.
 2. The heat transfersystem of claim 1, wherein the conductivity of the heat transfer fluidis about 0.02 to about 5 μS/cm.
 3. The heat transfer system of claim 1,wherein the liquid coolant comprises an alcohol, water, or a combinationthereof.
 4. The heat transfer system of claim 3, wherein the alcoholcomprises methanol, ethanol, propanol, butanol, furfurol,tetrahydrofurfurol, ethoxylated furfurol, an alkoxy alkanol, ethyleneglycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol,1,3-propylene glycol, dipropylene glycol, butylene glycol, glycerol,glycerol-1,2-dimethyl ether, glycerol-1,3-dimethyl ether, monoethyletherof glycerol, sorbitol, 1,2,6-hexanetriol, trimethylol propane, or acombination thereof.
 5. The heat transfer system of claim 1, wherein thenon-conductive polydiorganosiloxane antifoam agent comprises apolydiorganosiloxane emulsion based antifoam agent.
 6. The heat transfersystem of claim 1, wherein the heat transfer fluid further comprises anazole comprising a pyrrole, a pyrazole, an imidazole, a triazole, athiazole, a tetrazole, or a combination thereof, according to formulas(I)-(IV):

wherein R¹ and R² are independently a hydrogen atom, a halogen atomsuch, a C₁₋₂₀ alkyl or cycloalkyl group, SR³, OR³, or NR³ ₂, wherein R³is independently a hydrogen atom, a halogen atom, or a C₁₋₂₀ alkyl orcycloalkyl group, X is independently N or CR², and Y is independently Nor CR¹.
 7. The heat transfer system of claim 1, wherein the heattransfer fluid further comprises a non-ionic corrosion inhibitor, atetraalkylorthosilicate ester, a non-conductive colorant, a wettingagent, a biocide, a bitterant, a non-ionic dispersant, or a combinationthereof.
 8. The heat transfer system of claim 1, further comprising anion exchange resin in fluid communication with the heat transfer fluid.9. The heat transfer system of claim 8, wherein the ion exchange resinis pre-treated with a corrosion inhibiting composition comprising asiloxane corrosion inhibitor, an azole, or a combination thereof. 10.The heat transfer system of claim 1, in the form of an internalcombustion engine, a fuel cell, a battery, a solar cell, a solar panel,a photovoltaic cell, or a combination thereof.
 11. A heat transferfluid, comprising: a liquid coolant; a siloxane corrosion inhibitor offormula R₃—Si—[O—Si(R)₂]_(x)—OSiR₃, wherein R is independently an alkylgroup or a polyalkylene oxide copolymer of 1 to 200 carbons, x is from 0to 100, and further wherein at least one alkyl group and at least onepolyalkylene oxide copolymer are present; and a non-conductivepolydiorganosiloxane antifoam agent; wherein the conductivity of theheat transfer fluid is less than about 100 μS/cm.
 12. The heat transferfluid of claim 11, wherein the conductivity is less than about 25 μS/cm.13. The heat transfer fluid of claim 12, wherein the conductivity isabout 0.02 to about 5 μS/cm.
 14. The heat transfer fluid of claim 11,wherein the liquid coolant comprises an alcohol, water, or a combinationthereof.
 15. The heat transfer fluid of claim 14, wherein the alcoholcomprises a monohydric alcohol, a polyhydric alcohol, or a combinationthereof.
 16. The heat transfer fluid of claim 15, wherein the monohydricalcohol comprises methanol, ethanol, propanol, butanol, furfurol,tetrahydrofurfurol, ethoxylated furfurol, an alkoxy alkanol, or acombination thereof.
 17. The heat transfer fluid of claim 15, whereinthe polyhydric alcohol comprises ethylene glycol, diethylene glycol,triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,dipropylene glycol, butylene glycol, glycerol, glycerol-1,2-dimethylether, glycerol-1,3-dimethyl ether, monoethylether of glycerol,sorbitol, 1,2,6-hexanetriol, trimethylol propane, or a combinationthereof.
 18. The heat transfer fluid of claim 11, wherein the siloxanecorrosion inhibitor comprises a polysiloxane, an organosilane comprisinga silicon-carbon bond, or a combination thereof.
 19. The heat transferfluid of claim 11, wherein the non-conductive polydiorganosiloxaneantifoam agent comprises a polydiorganosiloxane emulsion based antifoamagent.
 20. The heat transfer fluid of claim 11, further comprising asecondary corrosion inhibitor.
 21. The heat transfer fluid of claim 20,wherein the secondary corrosion inhibitor comprises an azole, colloidalsilica, or a combination thereof.
 22. The heat transfer fluid of claim21, wherein the secondary corrosion inhibitor comprises the azole, andfurther wherein the azole comprises a pyrrole, a pyrazole, an imidazole,a triazole, a thiazole, a tetrazole, or a combination thereof, accordingto formulas (I)-(IV):

wherein R¹ and R² are independently a hydrogen atom, a halogen atomsuch, a C₁₋₂₀ alkyl or cycloalkyl group, SR³, OR³, or NR³ ₂, wherein R³is independently a hydrogen atom, a halogen atom, or a C₁₋₂₀ alkyl orcycloalkyl group, X is independently N or CR², and Y is independently Nor CR¹.
 23. The heat transfer fluid of claim 22, wherein the azole isselected from the group consisting of pyrrole, methylpyrrole, pyrazole,dimethylpyrazole, benzotriazole, tolyltriazole, methyl benzotriazole,butyl benzotriazole, mercaptobenzothiazole, benzimidazole,halo-benzotriazole, tetrazole, methyl tetrazole, mercapto tetrazole,thiazole, 2-mercaptobenzothiazole and a combination thereof.
 24. Theheat transfer fluid of claim 11, further comprising a non-ioniccorrosion inhibitor, a tetraalkylorthosilicate ester, a non-conductivecolorant, a wetting agent, a biocide, a bitterant, a non-ionicdispersant, or a combination thereof.
 25. A heat transfer method,comprising: contacting a heat transfer system with a heat transferfluid; wherein the heat transfer system comprises: a circulation loopdefining a flow path for the heat transfer fluid; and aluminum,magnesium, or a combination thereof; wherein the heat transfer fluidcomprises: a liquid coolant; a siloxane corrosion inhibitor of formulaR₃—Si—[O—Si(R)₂]_(x)—OSiR₃, wherein R is independently an alkyl group ora polyalkylene oxide copolymer of 1 to 200 carbons, x is from 0 to 100,and further wherein at least one alkyl group and at least onepolyalkylene oxide copolymer are present; and a non-conductivepolydiorganosiloxane antifoam agent; wherein the conductivity of theheat transfer fluid is less than about 100 μS/cm; and wherein thealuminum, magnesium, or combination thereof is in intimate contact withthe heat transfer fluid.